There are many voltage systems used for railway electrification around the world. Several railways in the world have an AC voltage higher than 10 kV and several lines with a voltage higher than 25 kV. Throughout the specification, these voltages, or other voltages higher than 10 kV, are referred to as “high”. Further, term “circuit breaker” shall mean “high voltage circuit breaker”.
Typically, a railway car connects to a power line via a pantograph, with the connection switchable by a circuit breaker. In such a field as electrical power distribution, the circuit breaker is often understood as a device which switches off the current in case of maintenance, short circuit tripping, or another abnormality. However, in the field of train electrification, the circuit breaker is a regularly operated controllable switch. The railway train circuit breaker must have high durability, since such a device is operated routinely and on a daily basis. A train circuit breaker may be required to perform several hundred-thousand switching cycles over its working life, a factor of more than a thousand times that required of circuit breakers in some other fields.
A conventional high AC voltage railway circuit breaker includes a pair of contacts in a vacuum. When the circuit is to be switched on, the contacts engage in mechanical connection. The vacuum enables switching of high voltages within a small and durable device that confines and minimizes high voltage arcing. Typically, the circuit breaker is placed on the roof of a train car and negatively affects train aerodynamics.